Compression ignition type engine

Abstract

A compression ignition type engine comprising a combustion pressure sensor arranged in the combustion chamber, wherein whether defective combustion is occurring or not is judged from a change in the combustion pressure and the air-fuel ratio is made larger when it is judged that defective combustion is occurring.

What is claimed is: 
     
       1. A compression ignition type engine comprising: a combustion chamber;   means for detecting an increase in an amount of inert gas in the combustion chamber over a range to a certain amount, wherein an amount of production of soot gradually increases over the range and peaks at the certain amount, and detecting an increase in the amount of inert gas in the combustion chamber beyond the certain amount, wherein a temperature of fuel and surrounding gas at the time of combustion in the combustion chamber decreases such that an amount of production of soot decreases;   means for providing an amount of inert gas to the combustion chamber that is greater than the certain amount;   defective combustion judging means for judging whether defective combustion is occurring; and   control means for controlling one of an air-fuel ratio and fuel injection timing so that combustion becomes good when defective combustion is occurring.   
     
     
       2. A compression ignition type engine as set forth in claim 1, wherein said control means makes the air-fuel ratio larger when defective combustion occurs. 
     
     
       3. A compression ignition type engine as set forth in claim 2, wherein said control means makes the air-fuel ratio gradually smaller toward a target air-fuel ratio determined by the operating state of the engine when good combustion is started due to the air-fuel ratio being made larger. 
     
     
       4. A compression ignition type engine as set forth in claim 1, wherein said control means makes the fuel injection timing earlier when defective combustion occurs. 
     
     
       5. A compression ignition type engine as set forth in claim 4, wherein said control means makes the fuel injection timing gradually later toward a target injection timing determined by the operating state of the engine when good combustion is started due to the fuel injection timing being made earlier. 
     
     
       6. A compression ignition type engine as set forth in claim 1, wherein a combustion pressure sensor is arranged in the combustion chamber and said defective combustion judging means judges if defective combustion is occurring or not based on a combustion pressure detected by said combustion pressure sensor. 
     
     
       7. A compression ignition type engine as set forth in claim 6, wherein a first peak of combustion pressure appears at substantially top dead center of a compression stroke, a second peak of combustion pressure appears after top dead center of the compression stroke, and said defective combustion judging means judges that defective combustion is occurring when the second peak pressure becomes lower than the first peak pressure. 
     
     
       8. A compression ignition type engine as set forth in claim 1, wherein detecting means is provided for detecting an amount of fluctuation of an output torque of the engine and wherein said defective combustion judging means judges if defective combustion is occurring based on the amount of torque fluctuation detected by said detecting means. 
     
     
       9. A compression ignition type engine as set forth in claim 8, wherein said defective combustion judging means judges that defective combustion is occurring when said amount of torque fluctuation becomes larger than a predetermined amount of fluctuation. 
     
     
       10. A compression ignition type engine as set forth in claim 1, wherein detecting means is provided for detecting an elapsed time required for a crankshaft to rotate by a predetermined crank angle including the explosion stroke of cylinders and wherein said defective combustion judging means judges if defective combustion is occurring based on the elapsed time detected by said detecting means. 
     
     
       11. A compression ignition type engine as set forth in claim 10, wherein said defective combustion judging means judges that defective combustion is occurring when said elapsed time becomes longer than an average value of the elapsed times of all of the cylinders by exactly a predetermined time. 
     
     
       12. A compression ignition type engine as set forth in claim 1, comprising means for detecting an engine rotational speed and, means for controlling a fuel injection amount so that the engine rotational speed becomes a target rotational speed at the time of idling. 
     
     
       13. A compression ignition type engine as set forth in claim 1, comprising means for detecting an air-fuel ratio and, means for controlling the air-fuel ratio to a target air-fuel ratio. 
     
     
       14. A compression ignition type engine as set forth in claim 1, comprising a control valve for controlling the amount of exhaust gas to be recirculated in an intake passage of the engine; means for calculating an exhaust gas recirculation rate; and means for controlling an opening degree of the control valve so that the exhaust gas recirculation rate becomes a target exhaust gas recirculation rate. 
     
     
       15. A compression ignition type engine as set forth in claim 1, wherein the means for providing includes switching means for selectively switching between a first combustion where the amount of the inert gas in the combustion chamber is larger than the certain amount of inert gas, and a second combustion where the amount of inert gas in the combustion chamber is equal to or smaller than the certain amount of inert gas, and a catalyst having an oxidation function and arranged in an exhaust passage of the engine is provided. 
     
     
       16. A compression ignition type engine as set forth in claim 15, wherein the catalyst is at least one of an oxidation catalyst, three-way catalyst, and NOx absorbert. 
     
     
       17. A compression ignition type engine as set forth in claim 15, wherein an exhaust gas recirculation apparatus is provided for recirculating exhaust gas exhausted from the combustion chamber into an engine intake passage and the inert gas includes recirculated exhaust gas. 
     
     
       18. A compression ignition type engine as set forth in claim 17, wherein the exhaust gas recirculation rate when the first combustion is being performed is at least about 55 percent. 
     
     
       19. A compression ignition type engine as set forth in claim 15, wherein an engine operating region is divided into a low load side first operating region where first combustion is performed and a high load side second operating region where second combustion is performed.